Rails of the above-described design type find a wide variety of applications, in particular in flexible drives of internal combustion engines. Rails of this type are used for force-transmitting or torque-transmitting drawing means, in order constantly to ensure a prestress which is sufficient for the functioning of the flexible drive. Rails of this type are usually arranged pivotably on a pin which is positioned in a stationary manner, in order to form a rotational bearing. A tensioning element, for example a compression spring or a hydraulically working apparatus, is assigned to the rail offset with respect to the rotational bearing. The hydraulically acting apparatus comprises a piston which, loaded by a hydraulic fluid pressure medium, exerts a force on the rail, in order thus to increase the tensioning of the drawing means. At the same time, the hydraulic tensioning apparatus includes a device which acts as pressure-limiting means and prevents a defined pressure being exceeded.
DE 42 12 309 A1 discloses a rail, with which a drawing means of a flexible drive is prestressed. The construction comprises a carrier element which is called an arm part and is connected to a shoe which performs the function of a sliding element. In the operating state, the rail is supported directly on the drawing means via the shoe. The shoe which is connected directly to the drawing means is manufactured from plastic. On account of the rail which is supported with a force-transmitting connection on the drawing means via the shoe, the said rail is subjected to wear independently of the lubricant conditions. For wear compensation, the rail is tracked via a spring means, a reduced prestressing force being set as the wear increases, with which prestressing force the rail bears against the drawing means. This can result in a critical wear state of the rail and the sliding element which is connected to it, as soon as the prestressing force which is set undershoots the prestressing force which is required for the functioning of the flexible drive. The reduced prestressing force at the same time leads to increased slip of the belt. In chain drives, an insufficient prestressing force of the tensioning system can lead to chain jumping between a chain sprocket and the chain, which causes consequential damage in timing drives, a flexible drive which is intended to drive a camshaft.